Biodigester systems are widely known in the art. Thousands of years ago, man found that it is possible to obtain methane gas, also called as biogas, and a potent organic fertilizer, also called as biol, from organic matter (cattle feces, human feces, blended fruits and vegetables, etc.) through its fermentation with anaerobic bacteria. In its simplest form, a biodigester system is a hermetically or tightly sealed container (also called anaerobic reactor or bag), within which said organic matter is stored, wherein said biodigester system further includes a certain mixture with non-potable water, so that the organic matter fermentation with anaerobic bacteria may produce said biogas and biol, thereby reducing the contaminating potential of feces, the attraction of insects, the generation of germs, and odors.
Biogas is a fuel capable of substituting fossil fuels or biomass (firewood). Biogas is produced from the decomposition of the organic matter, also called biomass, in a humid environment free of oxygen, by means of the bacteriological activity. Biogas is composed of approximately 60% methane (CH4) and 40% carbon dioxide (CO2). Biogas contains minimum amounts of other gases, including water (H2O) and sulfhydric acid (H2S). Biogas is somewhat lighter than air and has an ignition temperature of approximately 700° C., its flame reaches a temperature of 870° C., and it can be used as a fuel when the concentrations of methane are greater than or equal to 50%, as biomass has a high calorific value.
Biol is a liquid organic fertilizer produced from the decomposition of organic matter, such as animal manure, green plants, fruits, among others, in the absence of oxygen. Biol contains nutrients which are easily assimilated by plants, thus making them more vigorous and resistant. The technique employed to obtain biol is through biodigesters.
A common biodigester system is comprised by a reactor defined by a sealed bag storing the manure and/or organic waste, hereinafter called organic matter, for a period of time. Said reactor causes the biogas produced from decomposition to be stored and channeled for using the same. The common reactor is usually installed within a ditch at least partially enclosing said reactor by the ditch walls. The reactor includes an inlet whereby the organic matter enters the reactor, a biol outlet, and a biogas outlet whereby said biogas is channeled. The inlet and the outlet are usually sealed with a water seal. Due to the biogas density, the biogas outlet is usually located at the upper part of the reactor. The product obtained at each of the outlets is used, since biogas may be used as a fuel, and the biol is used as an organic fertilizer.
The technique to build the reactor has changed very little since the first biodigester systems were developed, changing only the membrane-type material used for manufacturing said reactor. At present, given its availability, it is common to use PVC as a manufacturing material for the reactor, since PVC is easy to get at an affordable price. In this regard, it is already known in the art that a direct contact with the sun's rays accelerates the manure decomposition process. However, PVC undergoes a short-term degradation as a result of said sunrays, so users cover the reactors, or create a sort of greenhouse for said reactors, thereby reducing the efficiency and increasing the implementation cost for biodigesters manufactured with PVC.
In the art, one way of manufacturing a reactor is by using two templates of impermeable material or membrane, with one template being an upper template and the other template being a lower template, wherein said templates have the same shape, usually an oval or circular shape. Thus, the upper template is placed on top of the lower template and said templates are joined together by sealing the templates at their contours or perimeters, defining a body whose interior may be inflated, forming a balloon (wherein said balloon takes the shape of the templates) for the subsequent introduction of the organic matter and/or the obtaining of biol through orifices with predefined dimensions. Another way known in the art of manufacturing a reactor is from three templates. The first template being a rectangular template forming a sleeve or pipe when the template longest parallel sides are joined together, said pipe being sealed by using at each end a circular template with a diameter that is equal to the diameter of said pipe. Therefore, in the end, when the reactor is inflated, the reactor design resembles that of a sausage.
In this regard, certain advantages have been found in the reactors manufactured from simple-shaped templates, i.e. from the joining of rectangular, circular, oval, or similar templates, because, when the organic matter is introduced and biogas starts to be produced, i.e. the heaviest liquid matter being at the lower part and the gas being at the upper part, said reactor inflates, thus generating different efforts and forming a plurality of creases in its perimeter or usually at the zones where the template joining is performed. The reactor surface where said creases are located is subjected to a plurality of undesired efforts on the material, since said zones will eventually exhibit leakages or tears, thus reducing the reactor lifespan, and representing a risk to users. Also, such creases may not be prevented even after the maximum inflation of the reactor, since this only increases the undesired efforts on the material, i.e. the creases remain, but said creases exert greater efforts on the material.
Therefore, it is desirable to obtain a biodigester system in which the reactor shape, when inflated, prevents the creation of creases and fits the content including substances of different densities.
Furthermore, it is desirable that said reactor is manufactured with a material that meets the characteristics of efforts, and that is also resistant to solar radiation.
In this regard, it has been found that the biogas thus obtained cannot be directly used by a user, since this gas contains hydrogen sulfide, which is highly corrosive and has significant amounts of water. Therefore, it is also desirable to obtain a biodigester system that includes filtrating and/or refining processes so that biogas can be used immediately.
It has also been found that there is a need to manufacture biodigester systems with different dimensions and capacities, wherein there is a direct relationship between the biodigester system size and the biodigester system biogas or biol production capacity. However, this variation in the user's needs makes it difficult to manufacture a standardized biodigester system, since several square meters of membrane are needed to manufacture a standard biodigester system. In this regard, it has been found that the users' needs change with time, and in certain cases this results in the user requiring to expand its biodigester system and also to expand the biodigester system capacities, including the land area required and the respective ditch. However, the technique currently used for the manufacture of biodigester systems does not allow for such expansion. Therefore, it is desirable a biodigester system which provides or not for the use of ditches to enclose the biodigester system reactor, thereby facilitating the implementation thereof, and which also provides for the use of interconnections between reactors to modularly expand the capacity of the original biodigester system. Thus, it is desirable to design a modular biodigester system whose manufacturing complexity does not rely on the size of said biodigester system and allows for future expansions, wherein the interconnection between different biodigesters is simple and provides an increase in the production of biogas and/or biol.
Finally, it is desirable to design a biodigester system which covers all the stages of the process, from the introduction of manure to the obtaining of biol or biogas, directly applied either to a stove, internal combustion engine or any other apparatus having the capacity to operate with said fuel.